I guess it could be a minor QoL update.
I can see there are some annoyances depending on your raiding schedule, but is it that big of a deal?
On the other hand:
Only enchanters that clear AQ40 have/need/have needed the tbc mats (e.g. even the CC rep Nature Resist on cloak pretty much implies that you're doing AQ40, Fire on the other hand, hmm...). If you have any of the high-end tbc-mat enchants on your enchanter, I'm pretty certain you would keep a stock of some tbc mats as well. This might give the tbc mats a little more value. If every enchanter can freely exchange the mats, the enchanter that clears AQ40 (the first boss...) loses a bit of their advantage. I like giving advantages to people if they do something more than others. Not having vellums and having disenchant rolls hurt the enchanting profession enough already in the moneymaking area, a slight conversion tip wouldn't hurt in my opinion.
Skeram is pretty nerfed right now, and a lot of AQ40 loot is still relevant. If you need access to the mats, chances are you are still doing AQ40 weekly. The absence of the tbc-mats does not block the ability to kill Skeram. Not having your enchant or a lower tier enchant in the mean time won't kill you.
Guilds have stocked up on tbc mats (or they should have), chances are that you can exchange them by talking to the right people.
"But there was no wall before!"
A lot of arguments can be made to Primal with a similar wording. A lot of things were possible before that are no longer possible. No real big actions were taken in the past to revert these things, so there shouldn't be any actions here either. If you smuggled lots and lots of mats past Skeram before, you just got lucky I guess.
"But I cannot make it to AQ40 runs anymore."
You can still ask someone you know and that trusts you to lend you their id. It's at a cost and a risk but hey. :^)
- Combat PVE / Subish PVP